How Hearthstone’s tech team tackles an online game for PC and mobile

Hearthstone: Heroes of Warcraft has 50 million registered players, making it the biggest hit in which players on PC and mobile are playing each other in the same game (this will eventually come to certain versions of Minecraft, which has 100 million in sales). But how do you make a user interface work for a game where you have people playing it on a powerful PC and a cramped iPhone screen — and against each other?

Jason Chayes is about to show us how.

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The production director for Hearthstone breaks down how Blizzard’s engineers tackle how to get a game’s interface work for both PC and mobile — and tweaking it to work on these different platforms (including tablet, which is different from a PC and from a smartphone). Here is an edited transcript of GamesBeat’s interview.

GamesBeat: People were wanting deck slots for a long time. Was mobile a roadblock to doing this, making it harder to code those additional deck slots in?

Jason Chayes: I wouldn’t say that was the biggest factor. It was a factor in that there’s a bigger challenge with how we make a UI that can accommodate the smaller amount of real estate on mobile devices. But I wouldn’t say that mobile by itself was why it took a little longer to get the deck slots feature out. What that came down to—we were never opposed to the idea of deck slots. For us the challenge was how to come up with an implementation that we were happy with that was still consistent with the values of Hearthstone. Meaning the charm and the accessibility of the game.

When we think about any of the features we’re working on, we think about them through those two lenses. How can we add this thing into the game that isn’t going to add so much additional complexity, so much additional overhead to the experience of playing that it starts to detract from the essence of what Hearthstone is all about? Finding the right way to do deck slots and making sure it was something that made sense was more of why it took the time it did to get there. I think we found a great solution. Players are going to be pretty excited when it comes out.

GamesBeat: I consider Blizzard’s programmers, coders, designers, some of the best in the business. How do they approach the challenge of making an app work both on the PC side and the mobile side in one game?

Chayes: That’s a big question. The way we approached it is we wanted to make the best possible experience on both platforms, or actually on all three platforms when you think about PC, tablet, and phones, all of which have slightly different UIs and different input mechanisms. We really think about what’s the best implementation of Hearthstone that we can make that works individually on each of those things.

We don’t want the version of Hearthstone that exists on the phone to just be a straight port of the PC version. We don’t think that would be the best experience. People who discover Hearthstone for the first time on a phone should have as good a response as if they’re discovering it through the PC. That was one of the major guiding philosophies. This is actually why it took an extra year after we shipped on tablet to get the phone version out.

Frankly, we didn’t know if we could make a phone version of Hearthstone at first. A lot of the initial few months was just doing prototypes to try to prove to ourselves that if we did a phone version of Hearthstone, it was going to be as good as all the other versions. We got to a point where we were happy with it. We had to make a lot of changes to the design, taking off a couple of corners, having the cards up on the board itself, changing the way the collection manager is represented. There’s a lot of little details there.

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That all said, given that we have those three separate platforms to work on, we still wanted the game to feel like one integrated experience. If I’m used to playing on my PC, and I switch to playing on my phone, it should feel like the same game. It should feel like the same Hearthstone. We didn’t want it to be the case that people couldn’t continue moving forward with their adventure progress or matchmake against the same people on their phone that they’re used to playing against on the PC. Our goal was to have them be customized per platform, but still have feature parity across all the platforms as well.

We started with that as the design vision, and then when it comes to the engineering side, a lot of the challenge was figuring out how to take our existing internal systems, for example Battle.net, which has only so far existed in the recent past on PC, and now start to extend that over to mobile devices. To do that, we’ve had to do a lot of things like figure out how to integrate with Apple’s systems, with Google’s systems, from a payment standpoint, the way we’re granting product, stuff like that. A lot of custom work goes into making sure we work across all of those. And our team is now set up so that we can support all those in parallel.

Related to the feature parity point, we wanted to make sure that if we were launching a new expansion or a new adventure, it’s available for all three simultaneously. A lot of the coordination that goes on is trying to understand the release implications of releasing on iOS and Android and trying to line everything up so that on one day, everything comes out at the same time.

GamesBeat: Is this a challenge that your designers and programmers relish?

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Chayes: There are days they relish it and days they pull their hair out because of it. It adds a lot more complexity. It also creates a lot more overhead as far as what a release looks like. Our goal with Hearthstone is to release very frequently, have new patches. A good example is Tavern Brawl, which comes out every week. The frequency with which we release new things, combined with the amount of surface area where we’re supporting all these different platforms and approaches, does mean a lot of challenge. I think we have a great team that’s executing amazingly well. The longer we do this, the more confident we feel in our ability to keep doing it more efficiently. Initially it was more challenging. We’re getting our stride a bit more now that we’ve been doing this for over a year.

GamesBeat: For the production side with Whispers of the Old Gods, what was the most difficult challenge you had with making it work on all these platforms, outside of C’thun?

Chayes: Thinking about the expansion itself—there are two ways I can answer that question. One is just the expansion itself, and one is where the expansion sits relative to everything else that’s happening in the game at the same time.

From the expansion itself, our biggest challenge legitimately was that we had too many good ideas. We had a bunch of card ideas that we think are awesome. We put so much into this particular expansion, we felt like we had to take some of the crazy ideas out and save them for future expansions, because there was so much that was already changing with Whispers of the Old Gods itself. We had to figure out how to scope it in a way that made this a great expansion, but at the same time didn’t go so overboard because of some of the other things that were happening at the same time.

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The other part of that question is that Whispers of the Old Gods is the first expansion coming out to coincide with the release of formats in Hearthstone. We talked about it this morning, but the separation now between Standard and Wild is coming out with this. There was a lot of production work that went into figuring out the implications of having Standard and Wild overlapping with the release of an expansion at the same time. A lot of that comes down to timing. How do we trigger the release of the expansion as it relates to the release of formats? Is it going to happen the exact same day the formats are available? What are the implications of them happening at the same time? What does it mean for players who come to the game for the first time? Working through all that timeline and making sure that it still makes sense for all of our existing and also our new players was one of the biggest challenges.

Normally, when we release a new card set, the card set comes out, and players have a chance to get a feel for the adventure, the expansion. This time, we had to make sure people not only understood what Whispers of the Old Gods was, but what does that mean for things like Standard mode and Wild mode? How does this new expansion relate to both of those? I think that’ll be easier in future releases. By that point people will have a better sense of what each mode means.

GamesBeat: It would have been easier to just release the formats and then the expansion, or vice versa. Why do it all in the same window?

Chayes: If we released the new formats before any new card content came out, then we think that for Standard mode, it wouldn’t be as exciting to build your new decks. You’d basically be having just a subset of all the cards that were already available. You’d be taking all of your existing decks and taking some of the cards out. That’s a downside of doing the formats first and the expansion later. Now let’s say we go the other way, do the expansion first. The problem there is, people will have built all their decks with Whispers of the Old Gods, plus intermixing a bunch of the Wild cards. By the time the formats come around, the decks will already be built, and so getting people to go through the process of re-creating their Standard decks and pulling out those cards also felt like a bad experience. We felt like the best possible way to do this was to release the formats and the expansions at the same time. Not only is everybody excited that all these new cards are available, but they can also use those new cards to make new decks in this new Standard format for the very first time.

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GamesBeat: Even if it was harder for you.

Chayes: It definitely created more challenges, for sure. That was a cost we paid. But we felt like it was the right thing to do for the game.